Remove extern declaration of __locale_cjk_lang in string/local.h

Now that __locale_cjk_lang is an inline function in setlocale.h and
setlocale.h is included, the declaration doesn't make sense.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

newlib/libc/string/local.h

@@ -4,10 +4,6 @@
 /* internal function to compute width of wide char. */
 int _EXFUN (__wcwidth, (wint_t));
 
-/* Defined in locale/locale.c.  Returns a value != 0 if the current
-   language is assumed to use CJK fonts. */
-int _EXFUN (__locale_cjk_lang, (void));
-
 /*
    Taken from glibc:
    Add the compiler optimization to inhibit loop transformation to library